The goal of this program Project is to understand the immunopathology of dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS), the severe complications of dengue virus infections. The frequency of DHF/DSS is much greater during secondary infections with dengue virus strains of a different dengue serotype than that which caused the primary infection. These immunopathological results have slowed down vaccine development because of safety concerns. The morbidity and mortality associated with severe dengue infections is a major public health problem which is increasing in frequency. We propose to define the molecular and cellular basis of the immunopathology associated with severe dengue infections.